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parvars

This folder contains an alternative version of the parametric example that uses parameter variables instead of the parameter/2 and this/1 built-in methods to access entity parameters.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the example:

logtalk_load(parvars(loader)).

Some queries using the list parametric object:

%%table
[1, 2, 3]::member(X).

<!-- X = 1 ; X = 2 ; X = 3 ; false. -->

[1, 2, 3]::last(X).

<!-- X = 3. -->

[1, 2, 3]::nextto(2, Y).

<!-- Y = 3. -->

\+ []::member(X).

<!-- true. -->

Some queries using the time and date parametric objects:

date(Year, Month, Day)::today.

<!-- Year = 2000, Month = 8, Day = 15. -->

date(Year, _, _)::today, \+ date(Year, _, _)::leap_year.

<!-- Year = 2002. -->

time(Hours, Mins, Secs)::now.

<!-- Hours = 13, Mins = 52, Secs = 42. -->

rectangle(W, H, X, Y)::init, rectangle(W, H, X, Y)::move(3, 4, NR), NR::position(X2, Y2).

<!-- W = 2, H = 1, X = 0, Y = 0, NR = rectangle(2, 1, 3, 4), X2 = 3, Y2 = 4. -->

Some queries with parametric objects that define "setter" methods that return updated object identifiers:

person(sally, 20)::grow_older(NewId).

<!-- NewId = person(sally, 21). -->

employee(sally, 21, 1200)::give_raise(250, NewId).

<!-- NewId = employee(sally, 21, 1450). -->

Some queries with parametric categories:

speech(winter, wedding)::advice.

<!-- Clothes: [pants, sleeves, heavy] Speech: [happy, jokes]

true. -->